Lesson 2: Energy
Tutorial
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Beginner
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+10XP
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60 mins
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(19)
Unity Technologies
Overview:
In this tutorial, you will learn about the relationship between mass, force, and energy as you calculate the velocity and acceleration of the cannonball on your worksheet. You will begin by opening lesson two and looking at how the mass and force sliders you used in the last lesson affect the energy involved in a catapult launching a projectile. When you’ve used your sliders to change the energy being used in your catapult, you will launch the ball and track the energy associated with the ball through its arc between the catapult and the ground. Using the law of conservation of energy, you will explain how energy is used and transferred by the catapult. Using one of the kinematic equations, you will be calculating the acceleration of your cannonball for two different sets of mass and force values. When you have finished with the lesson, you will move on to the boxes free play activity and track the energy needed to knock down all the boxes.
Project Outcome:
You will be able to explain the relationship between mass, force, potential energy, and kinetic energy. You will use kinematic equations to find the acceleration of a cannonball launched from a catapult. Using what you've learned, you will find the optimal mass, force, and energy needed to knock down a stack of blocks.
Learning Objectives:
By the end of this lesson, you will be able to:
- Adjust the mass of a cannonball and the force being used to launch it and understand the relationship between mass, force and energy.
- Understand the relationship between elastic potential energy and kinetic energy.
- Understand the relationship between the kinetic energy involved in the launch of a cannonball and the gravitational potential energy that a cannonball gains as it travels higher.
- Explain the relationship between the law of conservation of energy and the way a catapult launches a cannonball.
- Use a kinematic equation to find the acceleration of a ball as it launches from a catapult.
*Note: The law of conservation of energy and the kinematic equations can be found in the Formulas and More document.
Languages available:
1. Overview
In this tutorial you’ll change the force applied to the cannonball by the catapult and change the mass of the cannonball itself. You’ll learn how different forces interact with one another to change the trajectory of the cannonball and learn how to calculate the velocity of the cannonball depending on the values of the forces applied to it. Then, you’ll use your new knowledge to find the most effective way to knock down a stack of boxes with the cannonball!
2. Experiment with force and mass
In this section, you’ll learn about the different types of energy involved in the motion of an object.
Use the Cannonball Mass and Spring Force sliders to adjust the energy used by your catapult:
1. Enter Play mode.
2. Select the Lesson 2 [Energy] button and then the Proceed to Step 1 button.
3. Use the two available sliders to configure the mass and force settings of your catapult and observe how the elastic and gravitational energy values change.
4. After setting some values with the sliders, select the Proceed to Step 2 button and observe how gravitational potential energy changes as the arm on your catapult rises.
5. Select the Proceed to Step 3 button and observe the energy involved in launching your catapult.
6. Select the Continue button and observe how the gravitational potential energy changes as the cannonball progresses through its arc.
3. Document how the law of conservation of energy applies to a projectile.
In this section, you will repeat the steps from the previous section, but you will document your findings in the provided worksheet.
1. Enter Play mode and select the Lesson 2 [Energy] button.
2. Proceed through the steps with your own value settings like you did before.
We encourage you to try it a few times with different values. Pay attention to the energy values as the arm starts moving and note the difference between the elastic energy being used to lift the arm and the kinetic energy that is put into the cannonball.
3. Work your way through the steps again, but this time fill out the Lesson 2: Energy section of your worksheet and explain how the law of conservation of energy applies to the energy values through the launch of your ball.
Teacher Tip: The law of conservation of energy is outlined in the Formulas and More page. Record your answer on your worksheet.
4. Use a kinematic equation to find the acceleration of the cannonball
In this step, you will use the available information to calculate velocity and acceleration:
1. Enter Play mode and pick values for your cannonball mass and spring force as before.
2. Run the simulation and, in your worksheet, record the distance the cannonball travels and the velocity at the top of its arc in your worksheet.
3. Using the initial velocity you recorded and the gravitational constant, calculate the velocity of the cannonball at the top of its arc.
4. Using the distance and velocity you recorded and the kinematic equation, calculate the acceleration of the cannonball from the top of its arc to the ground.
5. Repeat the process one more time, this time using a different set of values for the cannonball’s mass and the catapult’s spring force.
Tip: The kinematic equations are listed in the Formulas and More page. Pick the one that allows you to find acceleration based on the time, initial velocity, and velocity at the top of the cannonball’s arc.
5. Knock down the boxes
In this section, you will use what you have learned to knock down a stack of boxes with the cannonball:
1. Enter Play mode and select the Free Play [Boxes] button.
2. Experiment with different values to find the settings that will allow you to knock down all the boxes.
More things to try
Find a way to knock down all 12 boxes with the lowest possible cannonball mass. Once you’ve done that, find a way to knock down all 12 boxes with the lowest possible spring force.